Urethane resin compositions utilizing moisture curing are widely used in various fields such as the vehicle field and the architecture field. In order to adhere a vehicle body and a window glass in the production of a vehicle, a primer composition is typically applied to the adhesion surface, and an adhesive is then applied thereon to attach the window glass to the vehicle body.
In primer compositions, considerable amounts of solvents are used to enable uniform coating, so from the perspective of the effects on workers or the effects on the environment, there have been proposed one-pack moisture-curing urethane compositions which make it possible to directly adhere a coated adherend (vehicle body) and a glass adherend without using a primer composition (for example, see Japanese Unexamined Patent Application Publication Nos. 2006-233218A and 2006-131802A).
Japanese Unexamined Patent Application Publication Nos. 2006-233218A describes a one-pack moisture-curing urethane composition which contains an isocyanate group terminated urethane prepolymer as a main component and can be adhered to a coated steel plate without using a primer by adding an appropriate amount of an aliphatic hydrocarbon compound such as polybutene or polyisobutene, which is a compound having a solubility parameter value from 6.0 to 9.0.
In addition, in Japanese Unexamined Patent Application Publication Nos. 2006-131802A describes a one-pack moisture-curing urethane composition which enables adhesion to a poorly adhesive coated steel plate without using a primer by establishing a specific relationship between the contents of a preliminary composition containing a urethane prepolymer, a filler, and a plasticizer, a specific adhesiveness-imparting agent, dimorpholinodiethylether, N,N-dimethylamino ethylmorpholine, 2-methyl-1,4-diazabicyclo[2,2,2]octane, and an organotin compound.
In particular, adhesive compositions for vehicles are required to be able to adhere a glass adherend to a poorly adhesive adherend such as a coated adherend without performing surface treatment by applying a primer, and also needs to be able to satisfy characteristics such as high-temperature/high-humidity adhesiveness, curing rate, flow resistance, storage stability, heat-resistant adhesiveness, and breaking elongation.
However, the one-pack moisture-curing urethane compositions described in Japanese Unexamined Patent Application Publication Nos. 2006-233218A and 2006-131802A have room for improvement in order to adhere a glass adherend to a poorly adhesive adherend such as a coated adherend without performing surface treatment and to be able to satisfy characteristics such as flow resistance, heat-resistant adhesiveness, and breaking elongation.